Aux shaft modification

[pope]

This is topic I thought was needed, especially after Jaime found a car he just bought with a cracked engine block and aux. shaft cracked in half. Even thought the 2.0's are considered non-interference for the pistons and valves, there still is a problem with the #2 rod and the end of the Aux. Shaft. when a belt breaks.



The part just to the right of the shaft, is the portion of the shaft the I cut with a cut-off wheel. The small item in the lower right corner is the plug that came out of the end of the cut off piece. The hole had been tapered, so the plug will not fit back into the new hole. I guess that you could find out what size hole the plug would accept and drill out the hole a little and use the same plug.
I then sanded and polished the cut end. I tapped the hole with a M8 x 1.25 tap (the remaining hole is the exact size for a M8 x 1.25 tap) and inserted an allen wrench installed screw. I applied thread compound and firmly tightened.

Thats it, no chance of parts hitting.

[mdrburchette]

Nice job Pope. It would have saved me a lot of time and money if I ran an electric pump and could cut off that lobe.

[wachuko]

Excellent thread Pope. This will help a lot of folks that do not require that lobe.

Do you know the purpose of that plug? Why did you have to plug it again?

Matt, from Vick Autosports, is sending me an aux shaft (THANK YOU!!!) and I would like to do the same mod, just curious as to why that plug is there and if you really need to plug it again. Easy to do, just wanted to know why.

[leeputmanjr]

Nicely done, Pope!

Now, I don't know the internal structure of the engine - but I thought it was the LOBE (one side being higher) that could hit one of the rod caps? I'd heard somewhere (God knows where) that the 'trick' was to put the aux shaft on a lathe, and trim that lobe down to where it was the same diameter as it's shaft.

Tell me I'm looney - 'cause this looks a LOT easier!

- Lee

[wachuko]

Nicely done, Pope!

Now, I don't know the internal structure of the engine - but I thought it was the LOBE (one side being higher) that could hit one of the rod caps? I'd heard somewhere (God knows where) that the 'trick' was to put the aux shaft on a lathe, and trim that lobe down to where it was the same diameter as it's shaft.

Tell me I'm looney - 'cause this looks a LOT easier!

- Lee

Lee,

The lobe is really an off-set/off-centered shaft in that Aux shaft... that is what Pope cut with the cutting wheel. When the off-set piece hits the rod it goes flying to the side of the engine block cracking it or just putting a hole through it.

I also thought this needed to be sent to a machine shop to remove... but if it is as easy as cutting it with a cut-wheel, well... even I can do that

Aux shaft end (should have taken a photo of the other side so you can see the piece that is off-centered.

[wachuko]

Well, it looks like the style of the lobe depends on the year, see photo:



Independent of that, the rest of the Aux Shaft seems to be the same, so the method of using the cutting wheel should still apply...

[manoa matt]

There is not much load on the aux shaft, so you don't need to cut it accuratly or ballance it. More people have access to hacksawas and cutoff wheels than metal lathes.

These are not my photos, I saved them from somewhere, I now can't remember where, but they show the before and after modifications to the shaft.

http://www.flickr.com/photos/bigtimes_fiat/4423015459/

http://www.flickr.com/photos/bigtimes_fiat/4423015457/

http://www.flickr.com/photos/bigtimes_fiat/4423015455/

There are two bearing journals, one at each end. There is a hole drilled through the center of the shaft that connects the two bearing journals. Oil is pressure fed directly to one of the bearings and lubes that bearing/shaft interface. Some of the oil goes into the shaft and travels along to the other journal bearing and lubes it.

If you just cut off the lobe and do not plug the hole, only one of the bearings will get oil and the other will sieze up.

Most people will drill and tap the hole, I've heard of a few guys re-using the original plug. Your oil pressure may get as high as 90psi at high revs so making sure the plug is secure is very important.

The lobe size is related to the mechanical fuel pump actuating arm. Early cars were smaller displacement and required less gas. I'd have those shafts measured up accuratly. They look similar, but may not be as universal as you think.

[pope]

The reason the plug is there originally is that thats the end there they drilled the oil hole through the shaft to feed the two bearings.
You can see in the first pic, that the lobe is off center from the hole. I threaded the hole to make sure the end stays put. There are no Balance worries with this method. I could not find a new plug to fit the new hole. You will have to redrill the hole larger to use the original plug.

[narfire]

Pope, thats what I do after wacking the end off. Drill out the passage, clean and dry and tap the plug in with some JB. No issues so far,touch wood, on either engine I did the mod on. I can't remember the dill bit size though.

[manoa matt]

Whatever, just cut it and plug it.